Ultrasound-guided recurrent laryngeal nerve block is useful in the diagnosis and treatment of painful conditions subserved by the recurrent laryngeal nerve, including posttrauma pain in the region, as well as painful conditions of the larynx and pharynx below the glottis and pain of malignant origin (Fig. 24.1).

The recurrent laryngeal nerves arise from the vagus nerve. The right and left recurrent laryngeal nerves follow different paths to reach the larynx and trachea. The right recurrent laryngeal nerve loops underneath the innominate artery and then ascends in the lateral groove between the trachea and esophagus to enter the inferior portion of the larynx (Fig. 24.2). The left recurrent laryngeal nerve loops below the arch of the aorta and then ascends in the lateral groove between the trachea and esophagus to enter the inferior portion of the larynx (Figs. 24.3 and 24.4). It is at this point when traveling superiorly in this lateral groove between the trachea and esophagus at the level of the first tracheal ring that the nerve is most accessible for neural blockade (Figs. 24.5 and 24.6). The recurrent laryngeal nerves provide the innervation to all the intrinsic muscles of the larynx except the cricothyroid muscle as well as providing the sensory innervation for the mucosa below the vocal cords. The nerve is susceptible to damage during thyroid surgery and compression from tumors.

The patient is placed in the supine position with the head in neutral position. Three milliliters of local anesthetic is drawn up in a 10-mL sterile syringe, and 40 to 80 mg of depot steroid is added to the local anesthetic if there is thought to be an inflammatory component to the patient’s pain symptomatology. The medial border of the sternocleidomastoid muscle at the level of the cricothyroid notch is identified by palpation as is the first tracheal ring just below it. A high-frequency linear ultrasound transducer is then placed over medial border of the sternocleidomastoid muscle in the transverse position at the level of the first tracheal ring (Fig. 24.7). In patients with thinner necks, an acoustic standoff of ultrasound gel may be needed to optimize image quality. The trachea and esophagus are then visualized and the relative position of the carotid artery is noted (Fig. 24.8). Color Doppler is then utilized to further delineate the carotid artery as well as to identify any significant vessels including branches of the thyroid artery that could be injured during needle placement. The recurrent laryngeal nerve is located in the lateral groove between the trachea and esophagus and may be identified on ultrasound as a monofascicular hypoechoic bundle with a hyperechoic perineurium in some patients (Fig. 24.9). Longitudinal ultrasound views may help confirm the identification of the nerve (Fig. 24.10).